Update to latest package:stagehand
Update to latest package:stagehand

Switch to importing by SHA rather than tag and sync before publishing.

Change-Id: Ibf563c4fc28f6b4a08b29feee24d4f7cc234ef27
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/176920
Auto-Submit: Nate Bosch <dc212c74d8afde9c690fdd09e74d3e5c5d5a3de0@google.com>
Commit-Queue: Nate Bosch <dc212c74d8afde9c690fdd09e74d3e5c5d5a3de0@google.com>
Commit-Queue: Jacob Richman <5a36c29261d3132fd40b770145a0522ecd2a93e0@google.com>
Reviewed-by: Jacob Richman <5a36c29261d3132fd40b770145a0522ecd2a93e0@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk